with it in a vise clamped easy with wooden blocks use a 3/8 flat punch & drive the lower one out first, tap around the circumference of it & use care then turn the housing over drive out the top bushing the same way. soak the new ones in oil for 15 minutes & use a bushing driver & drive the lower one in till flush with the housing & the top one in till it is 1.163" down from a straight edge across the top of the dist perimeter that the cap sets on. Polish the shaft lightly with some 400 grit emery or crocus cloth to remove any burrs or varnish buildup then oil the shaft & insert it & if it binds, you would need an adjustable bushing reamer used with care. set lower shaft end play to .005" & speedway mtrs has a kit of flat shims for $10 to go above the nylon collar. EDIT best would be to have your best machinist press em out expecially if it is a number matching dist.